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How to tell the difference visually on BNC connectors
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TerraHertz:

--- Quote from: opablo on March 26, 2013, 04:54:47 pm ---Just to help others save a valuable click, here is the image from wikipedia...

--- End quote ---

Ah ha. Learn something every day. Till this moment I had no idea there were different impedance BNC and N standards. I'd just assumed for BNC people put up with the 75/50 mismatch in video systems, and that N connectors only ever used 50 ohm cable.

Checking, I find I have some 75 ohm BNCs that are different to that photo. Will post a pic later. Got to go out now.
dexters_lab:
i have seen 50ohm BNCs which look like the 75ohm versions too, that wiki picture is not the whole story

IdahoMan:

--- Quote from: dexters_lab on September 06, 2016, 08:52:40 am ---i have seen 50ohm BNCs which look like the 75ohm versions too, that wiki picture is not the whole story

--- End quote ---

And vise-versa? Here's a site that is selling claimed 75ohm BNC adapters, but they look 50ohm..?

IM

dmills:
At the sorts of frequencies and power levels most folks use BNC for it is not usually a huge deal (Outside of broadcast, where for mainly historical reasons we cart 3Gb/s serial digital video around on the 75 ohm versions).
Sometimes someone gets an attack of the stupid and tries to do 6Gb/s or even 12Gb/s over the same cables, that is when the money for Pasternack or Huber & Schurner makes sense.
CCTV of the composhite type is all so low frequency that you would have to really work at it to get a connector impedance discontinuity to cause a problem.

I had to laugh at the notion of a specifically 75 (or 50) ohm BNC to RCA, them things tend to be nothing in particular impedance wise.

The things that matter more on BNCs IME is using the right one for the cable and the right tooling when crimping the things, a poor crimp will cause far more pain then a 50 ohm BNC in a 75 ohm system.

The good stuff for RF is always expensive, as it is in every field, have a look at VNA calibration kits or precision attenuators if you want to see really silly pricing.

Regards, Dan.
helius:
It should be kept in mind that at the frequencies carried by baseband analog video, you would need a very long cable before the reflections from the 50 ohm-75 ohm mismatch were visible. The way that video systems are designed, BNC connections are rarely used for RF.
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